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When Temporal Investigations arrives on Deep Space 9, Sisko recounts how he and the crew of the Defiant traveled back in time to the 23rd century to prevent the assassination of Captain James T. Kirk during the original Enterprise's mission to Space Station K-7.

Sisko asks if they want anything to drink; they say they only want the truth. Dulmur asks Sisko why he took the USS Defiant back in time. Sisko says it was accidental and he confirms that he is not contending their trip back was a predestination paradox, a statement which relieves the investigators, as they hate predestination paradoxes. When they ask him to start at the beginning, Sisko tells them this may take some time and then assures them that he's not cracking a joke, something the investigators say they hate as well. Sisko tells them that the Cardassian government had expressed a desire to return one of the BajoranOrbs that they had procured during the Occupation, so the Defiant traveled to Cardassia Prime – under cloak to avoid detection by the Klingons – to collect it, without knowing which orb it was or even if it were genuine, as many counterfeit orbs had emerged over the years. Though they were unaware of this at the time they recovered it, they had indeed gained possession of the Orb of Time. Sisko had security lock the Orb in crew quarters so it could be authenticated on Bajor. Before leaving Cardassia Prime, they took on a passenger.

CommanderWorf brings a man into the Defiant's mess hall who, upon seeing ChiefO'Brien and Dr.Bashir, expresses his relief to finally see Humans again. Worf introduces the man as Barry Waddle, a Human merchant who had been trapped on Cardassia when the Klingons attacked. He is an elderly, seemingly harmless man. Waddle says he deals in gemstones, mostly kevas and trillium. While he orders a raktajino from the replicator, he tells O'Brien and Bashir about how Cardassians drink hot fish juice in the morning and that after being on Cardassia for a time, he was hoping for a Klingon invasion as they can make good coffee, even if they are foul-smelling barbarians. He then notices Worf is right there, apologizes to him, and steps away. O'Brien and Bashir gently tease Worf about his aroma, telling him he has a rather earthy, peaty aroma with a touch of lilac – which only serves to annoy Worf further.

The Enterprise appears

On the bridge, as Defiant is halfway back to Deep Space 9 and Sisko tells the investigators that he was finally beginning to relax, O'Brien relays the story of the incident in the mess hall to Dax and suggests that she mention lilac the next time she sees Worf, but she refuses, saying she has her own ways of torturing him. At that moment, O'Brien announces a massive surge in chroniton radiation around the ship as the entire bridge glows brightly. The viewscreen shows nothing but white noise. The ship drops out of warp and decloaks as someone activates the transporter. Sisko orders Dax to get the ship back under cloak and deactivate the transporter, but it is already too late, as the person has already left the ship. Just then, as the ship gets back under cloak, Dax tells Sisko that they are now over two hundred light years from their previous position. Sisko orders the viewscreen activated and the sight they see on the screen shocks them all; a Constitution-class starship, marked NCC-1701... USS Enterprise.

In Sisko's office, Dulmur asks him to specify which Federation starship Enterprise as there have been five, but Lucsly quickly corrects him, saying there are now six. Sisko clarifies that it was the first Enterprise, the Constitution-class, NCC-1701. The investigators sit back in their seats in horror at the realization it is "his" ship, James Kirk's, which Sisko proudly confirms. The investigators both call Kirk a menace, saying that Kirk's file, containing seventeen separate temporal violations, is the biggest on record. They ask what the Enterprise was doing and Sisko says it was orbiting one of the old deep space stations, K-7, exactly one hundred and five years, one month, and twelve days previous, on Stardate 4523.7, a Friday.

Sisko's story continues. Back on the Defiant, a briefing is occurring with the senior staff. Worf and Odo have discovered that Waddle's "real" name is Arne Darvin, a Klingon surgically altered to appear Human. Worf tells Sisko that the younger Darvin is, at that moment, on board K-7, posing as a Federation official. Odo picks up and tells Sisko that the younger Darvin's mission was to derail Federation colonization efforts in the area by poisoning a load of grain which was – or rather, is – stored on K-7. However, in eighteen hours, Captain Kirk will expose Darvin and he will be arrested. Worf tells them that Darvin's arrest ended his career, as Klingon Intelligence turned their back on Darvin and he became an outcast, apparently spending the next hundred years posing as a Human merchant and then in what Odo calls a "final indignity," he was trapped on Cardassia by the Klingon invasion. Sisko then is able to pick the story up from there. Apparently Darvin then heard rumors about an Orb capable of taking him back in time. Bashir wonders if Darvin may be going to warn his younger self about Kirk, but Dax thinks Darvin may be planning to kill Kirk. And not knowing how or where or when, Sisko decides that they will have to search both K-7 and the Enterprise without raising suspicions or altering the timeline themselves, as he ironically notes that the last thing he wants is a visit from Temporal Investigations when they get home.

So the crew starts to blend in. Odo and Worf change into civilian traders' clothing, and Sisko, Dax, O'Brien, and Bashir all change into old-style Starfleet uniforms with Dax taking the extra precaution of applying makeup to cover her spots.

Stepping out into the corridor, Sisko, who is now wearing a gold command uniform with lieutenant's stripes, sees Bashir, still in sciences blue, albeit with an appropriately altered hairstyle, Sisko tells him that he went with lieutenant's rank because he didn't want to arouse suspicion. Just then, O'Brien appears in a red support uniform, with ensign's insignia, and Bashir asks if Sisko and O'Brien are wearing the wrong colors. O'Brien asks if Bashir knows anything about this time period, and he says that he doesn't, as he's a doctor, not a historian. Sisko clarifies that the colors were switched in Kirk's era. Dax then appears in the miniskirt uniform of the day (though in operations red rather than her usual sciences blue), saying that "women wore less," and the doctor, unsurprisingly, declares that he will like this time period.

In the transporter room, O'Brien reports that the old-style sensors the Enterprise used allow for tiny interruptions in the scan cycle enabling the Defiant to decloak for three seconds and beam everyone to where they need to go. Worf and Odo are sent to K-7. Worf reports that most of K-7 consists of storage areas and industrial fabrication facilities and, since security on a space station such as K-7 is not as tight as it would be on a starship, they do not expect to have to take long to search the station. The other four go to the Enterprise, O'Brien and Bashir together and Dax and Sisko together, each pair to opposite ends of the ship. After reminding everyone to do their best not to interact with people from this time period, Sisko and Dax go first, beam into a turbolift and step out into a corridor on the Enterprise.

Bashir and O'Brien beam into another turbolift and try to proceed to Deck 21. O'Brien's vocal command goes unheeded and, not knowing what could be wrong with the turbolift, they try to take a panel off to see what's happening when they're interrupted by the lift's doors opening. A woman steps in, nods to O'Brien and Bashir, takes one of the handles on the side of the turbolift and orders it to Deck 15. Sheepishly, O'Brien and Bashir take hold of the handles near them and Bashir whispers to O'Brien, "I won't tell anyone if you won't."

Dax marvels as to how many people are packed into the ship. Finding an auxiliary communications juncture, Sisko pretends to do repairs and Dax admires the "classic" 23rd century design of the tricorder she carries, but Sisko quiets her before she attracts anyone's attention.

On K-7, Odo steps into the station's bar and sits down at a table. As he does, the door opens again, admitting EnsignChekov and LieutenantUhura into the bar. As they walk up to the bar, a waitress asks Odo what he would like to drink; he tries to order raktajino. When the waitress tells him he is the second person who ordered that today, he asks who the other one was; she says that it was an elderly Human male. She tells Odo that he said he would probably be back later. Then, after being informed that raktajino is Klingon coffee, she tells Odo they have no Klingon beverages, and so he settles for Tarkalean tea. As he sits at the bar and watches, he sees Uhura obtain a tribble from Cyrano Jones.

Back on the Enterprise, Bashir continues to scan for Darvin. O'Brien is supposed to be conducting repairs so as to blend in, but unfortunately he cannot tell what is what, as all is cross-circuited and rewired. Bashir jokes that it sounds like one of O'Brien's repair jobs. Both are then interrupted by a young engineer who wonders why they are working at that panel, because Scotty had told him to do it. He then wonders why they need a doctor to repair a power relay. Bashir makes up a story about checking O'Brien for stress and, after O'Brien accidentally pulls out a circuit that darkens the whole deck (and quickly replaces it) tells O'Brien he has seen enough and that they need to go to sickbay. O'Brien tells the engineer he would appreciate if he did not mention this to anyone. The engineer says he will not, and expresses his hopes that O'Brien feels better soon.

On K-7, Worf enters the bar and sees Odo sitting at a table. Worf tells Odo he has finished searching the primary habitat levels. Before he can get any farther, he notices a trilling sound and demands to know, "What is that noise?" Odo says the sound is very soothing; he holds the tribble up as it squeals at Worf, who disgustedly recognizes it.

Odo has Worf sit down before he attracts any further attention. Sitting down, Worf asks where Odo got it; he tells Worf that he got it from one Cyrano Jones, who said that tribbles like everyone – but apparently not Worf, a feeling which Worf shares. He calls the tribble a "detestable creature," noting that feeding a tribble more than the smallest morsel will cause prolific reproduction. Worf tells Odo how tribbles were considered mortal enemies of the Klingon Empire, which Odo is amazed to hear, finding it hard to believe that a simple tribble could be someone's "mortal enemy." Worf further explains that the Empire considered tribbles to be an ecological menace and that many warriors were sent out to kill any and all tribbles that they could find. Once the tribble homeworld was located, a Klingon armada obliterated it. According to Worf, tribbles were considered extinct by the end of the 23rd century, which Odo sarcastically calls "another glorious chapter in Klingon history," and then proceeds to ask Worf mockingly, "Tell me, do they still sing songs about The Great Tribble Hunt?"

Before Worf can say anything else, the station goes to red alert. The same has happened on the Enterprise. Seeing everyone rush to battle stations, Dax asks Sisko what they should do; he says they should do the same. They find an empty turbolift and Sisko contacts the Defiant, or at least he tries to; he slaps the insignia on his uniform out of habit, expecting it to be the working combadge that it is not. After a moment of realization, he pulls out the old-style communicator and this time successfully contacts the Defiant. Kira reports that a KlingonD7-class battle cruiser has dropped out of warp and is approaching the station. Recognizing something familiar, Dax asks Kira to identify the Klingon vessel; she identifies it as the IKS Gr'oth. Dax immediately recognizes it as Koloth's ship and she tells Sisko that Koloth is not here to attack. She remembers Koloth telling her about how he once traded insults with Kirk on a space station near the Federation-Klingon border and how he regretted never getting to face Kirk in battle. Kira then reports that the Klingons just beamed two people to the station manager's office. Dax remembers one of them being Koloth, and asks Sisko if they could beam over to K-7, as they know that Darvin was there a short time ago. However, Sisko refuses and tells Kira to contact O'Brien and have him and Bashir prepare to transport to the station. Dax wants to see Koloth and points out that it is not as if he would recognize her, but Sisko stands firm. After closing the channel with Kira, Dax says it would have been fun, but Sisko corrects her: it would have been "too much fun."

Sisko informs the investigators that Dax was indeed correct. The Klingons only wanted shore leave, and Captain Kirk allowed the Klingons to beam over in small groups. Once the red alert ceases, everyone resumes their search for Darvin.

Kira contacts O'Brien and Bashir on the Enterprise, telling them the next band shift in the Enterprise's scan cycle is coming up. O'Brien tells her they will be ready. He and Bashir duck into a turbolift, but Lieutenant Watley is there with them again. She notices that Bashir has left the flap open on his tricorder, thereby draining power. He closes it and thanks her for the tip. Watley asks Bashir if he is a doctor; he replies in the affirmative. She says that she just transferred over from the USS Lexington and O'Brien, acting as a regular member of the crew, welcomes her aboard. Watley tells Bashir that she will be in sickbay the next day at 15:00 hours for her physical, and tells him her name as she walks out of the turbolift. Bashir recognizes her name as his great-grandmother's last name and wonders if it could be her, which O'Brien scoffs at, as the odds of that happening are astronomically small. Since no one ever met his great-grandfather, he then begins wondering if he is supposed to meet with her later in a predestination paradox and become his own great-grandfather. O'Brien accuses Bashir of being ridiculous, but he begins to convince himself that if he does not meet with Watley, he may not ever even be born. Just then, Kira calls and asks O'Brien if they are ready for transport; the Chief's reply: "Are we ever!" Bashir denies being able to wait to get back to Deep Space 9 and watch O'Brien's reaction when he finds out Bashir was never born, a comment which causes a smirk from O'Brien as they beam out.

Kirk, Spock, Sisko and Dax

Elsewhere on the Enterprise, Sisko and Dax are near another panel, pretending to work on it, when Dax looks up, sees Captain Kirk and Commander Spock walking toward an intercom close to them, and gets Sisko's attention. They look for a moment. Then Sisko reminds her they are supposed to be only maintenance crew members doing their jobs. But Dax cannot help looking as Kirk deals with the intercom transmission. She notes how he is so much more handsome in person; Sisko tells Dax how Kirk had a reputation for being a ladies' man, but she reveals herself to be referring to Spock instead. At that, Sisko closes the panel, takes Dax by the hand, and they walk away from Kirk and Spock. Dax is amazed that Sisko does not want to meet Kirk. Sisko calls that the farthest thing from his mind, as they have a job to do. Dax then reminds Sisko about how Kirk is one of the most famous captains in Starfleet history. Sisko then admits that indeed he would like to meet Kirk, shake his hand, and ask him about fighting theGorn on Cestus III. That, however, is not the reason they are there. Dax concedes Sisko's point, but laments that as she remembers this time period, it is difficult for her not to want to be part of it again. At that point the turbolift opens and they enter.

Bashir and O'Brien enter the bar on K-7, whereupon they good-naturedly tease Odo and Worf for sitting at the bar while they were crawling through conduits on the Enterprise and the station. Odo says they believe that Darvin will return and Bashir picks up on the raktajino hint, a clue that others might have missed. Before they can say anything else, Chekov, Scotty, and Freeman enter. O'Brien is amazed, having mistaken Freeman for Kirk. Worf agrees that it would be an honor to meet Kirk. O'Brien suggests buying Kirk a drink, but Odo reminds them they cannot, and O'Brien agrees, as altering the time line would be too great a risk to take. The waitress comes up and asks them what they want, including a warning not to dare ask her for a raktajino. She then points out the Klingons when Odo asks who else had ordered a raktajino, but they fail to recognize the Klingons as such, since they look nothing like Worf or any other Klingons that the crew had met. When they act confused, the waitress decides they have had enough and walks away. Everyone at the table then looks over at Worf, wondering what's going on. Worf tells them that those are Klingons, and that it is a long story that Klingons do not discuss with outsiders. Meanwhile, a Klingon named Korax has spent his time loudly insulting Kirk, trying to get a rise out of the Enterprise officers. Chekov stands up to fight, but Scotty restrains him, saying they can take a few insults. O'Brien is impressed at how "Kirk" (Freeman) is ignoring Korax. At that moment, a confused Bashir asks if that is really Kirk, and O'Brien says it is, but then Bashir points out that the man is only wearing lieutenant's stripes. Odo says they have more problems at the moment than a case of mistaken identity. Just then Korax begins insulting the Enterprise herself, which quickly gets under Scott's skin – he is the engineer, after all. When Korax, who had called the Enterprise a "sagging old rust-bucket designed like a garbage scow," clarifies his statement by claiming, not that the Enterprise should be hauling garbage, but instead that it should be hauled away, as garbage, Scott slowly stands up and punches him. Every Klingon and Starfleet officer stand up immediately and then, despite Odo's efforts to stop them, Bashir, O'Brien, and Worf all stand up. Everyone ends up in the huge brawl in the bar. When the door opens to admit more Enterprise security, Odo notices Darvin in the background and knocks a Klingon off of Worf so they can both give chase to Darvin. Meanwhile, caught up in the fight, Bashir and O'Brien fail to notice Worf and Odo's departure and are themselves, shortly thereafter, arrested by the security officers and taken into custody along with the other crew members who were involved.

In Sisko's office, the investigators are not happy, as regulations clearly state that Starfleet officers must take all precautions in taking minimal part in historical events. Sisko admits that they made a mistake, but it caused no alteration of the timeline. Dulmur is not so convinced, and goes so far as to point out that this could be an alternate timeline as far as they know, but Sisko says that if they had altered history, they would have known immediately upon their return. After exasperatedly wondering out loud why everyone he interviews always has to mention that particular fact, Lucsly bids Sisko to continue.

Kirk questions a group of officers that includes Bashir and O'Brien

Sisko tells them that instead of going to the brig, the arrested officers were taken in for questioning. Bashir and O'Brien find themselves in a line in front of Kirk, who wants to know who started the fight. Kirk asks O'Brien who started the fight; O'Brien tells Kirk he does not know. Likewise, Chekov tells Kirk he does not know who started it. When no one confesses, Kirk confines everyone to quarters until he finds out who started it. After they are dismissed, O'Brien and Bashir walk away as quickly as possible. O'Brien is astounded that, of all the people in the lineup, Kirk asked him about the fight and that, even more astonishingly, he ended up lying to him! O'Brien says he wishes Keiko could have seen it. Accidentally stepping on a tribble, Bashir wonders who left it out in the corridor alone. But rounding the corner, O'Brien realizes that the tribble is actually far from alone.

Meanwhile, Odo and Worf have captured Darvin in the midst of the fight on K-7 and have beamed him back to the Defiant. Odo tells Darvin that he will face some very serious charges when they return, but Darvin says they would not dare put one of the greatest heroes of the Klingon Empire in the brig, to which Worf angrily tells Darvin he is no hero to the Empire. But Darvin says he will be soon, and wants his statue in the Hall of Warriors to have him standing with Kirk's head in one hand and a dead tribble in the other. Worf grabs Darvin and demands to know what Darvin did: did he hire someone to kill Kirk, or sabotage the Enterprise? But Darvin says that though he did nothing like that, Kirk's death will have a certain poetic justice to it.

Shortly thereafter, Sisko, who is still on the Enterprise with Dax, is amazed to hear from Odo that Darvin has planted a bomb in a tribble. Odo describes it as revenge from Darvin, as in the original timeline Kirk noticed how a tribble reacted to the younger Darvin and realized he was a Klingon. While Darvin has obviously refused to reveal the bomb's location, he did say it was set to go off within the hour. Dax suggests they risk going to the bridge and using the internal sensors to scan the ship within minutes. Sisko agrees and orders everyone else to K-7 to search for the bomb. However, Odo suggests that Worf remain on the Defiant due to his mutual dislike of tribbles, to which Sisko agrees. However, O'Brien is concerned they may not be able to reach the station's internal sensors. Sisko tells him that then he will have to manually scan every tribble on the station. O'Brien, in disbelief, says there must be thousands. Bashir notes it could be hundreds of thousands, but Dax has already worked out the number as one million, seven hundred and seventy-one thousand, five hundred and sixty-one, starting with one tribble, producing an average litter of ten every twelve hours over a period of three days. Sisko tells everyone they have their orders and closes the channel.

Later on the bridge, Sisko is sitting at a station and Dax is standing over by the engineering station when Kirk comes onto the bridge. He tries to sit in his chair, but ends up accidentally sitting on a tribble. Removing the tribble Kirk looks over at Dax who smiles and shrugs at him. He then calls Dr. McCoy to the bridge. Dax steps over and tells Sisko that she has reworked the sensor interface. Sisko scans the bridge. No explosives are found, which relieves Dax as she almost expected the tribble Kirk sat on to explode. Nothing is found on the first six decks either. Just then, McCoy comes up to the bridge and begins talking to Kirk. Dax seems to recognize him and Sisko identifies him as McCoy, the ship's doctor. Just then, Dax recognizes him, having met him when he was a medical student at "Ole Miss." Sisko asks if it was Curzon who met him; she says it was actually Emony, when she was on Earth judging a gymnastics competition. Dax tells Sisko that McCoy had the hands of a surgeon and that she knew he would be a doctor. Her smile suggests their acquaintance might have been more than purely social. Sisko is rescued from having to respond by the completion of the scan– there are no explosives aboard. Dax, stating the obvious, says that the bomb must be on K-7.

In the bar on K-7, Odo, Bashir and O'Brien are searching through tribbles frantically when Odo gets a call from Sisko telling them the bomb is not on the Enterprise – thus, it must be over there. Unfortunately, Odo reports that they have been able to scan only two decks so far. When Sisko offers to send more people over from the Defiant, Odo tells him it is no man-power shortage; rather, it is that the tribbles are multiplying so fast that they cannot keep up with them. Dax suggests that she and Sisko stay close to Kirk, as Darvin likely will have put the bomb someplace he knows Kirk will be in the next half hour and, as a result, Kirk may lead them right to it. Odo says they will keep scanning the tribbles for now.

Sisko and Dax get set up in the recreation room when Kirk and Spock come in. Kirk, upon ordering his chicken sandwich and coffee, sees that the tribbles are in all the food slots. Kirk tells Spock, "I want these things off the ship. I don't care if it takes every man we've got; I want them off the ship!" Scott comes in with an armful of tribbles and tells them the tribbles are in the machinery and probably in all the other food dispensers as well, probably having gotten there through one of the air vents. Spock realizes there are similar vents on the station... "and in the storage compartments!" Kirk realizes, interrupting him. Sisko is given a clue then, and he and Dax beam to K-7 and climb down into one of the storage compartments to begin scanning tribbles. Sisko notes that most of the tribbles are dead, as the grain has been poisoned. Dax detects a faint tricobalt signature, indicating the bomb is in the compartment somewhere. They begin scanning through the tribbles when they hear a strange, multi-toned beeping sound. As it turns out, that sound is Kirk, outside, trying to open the hatch leading into the storage compartment. He finally does get it open – and ends up being buried in tribbles. Sisko and Dax see the hatch open, and as it turns out, Kirk's opening the hatch all but exposes the bomb in the storage compartment. Dax realizes it is directly in front of them. Sisko begins searching frantically for the bomb, tossing tribbles away as he scans them, some of them falling through the doorway and landing on Kirk. Down on the floor, Nilz Baris threatens to hold an inquiry against Kirk, stating there must be thousands of tribbles. Kirk laments it must be hundreds of thousands. Spock comes up with an exact figure of 1,771,561, using the exact formula that Dax had used earlier. In the hold, Sisko and Dax hear this, look at each other and simply shrug. Just then, Sisko finds the bomb. He places the tribble bomb on his tricorder, contacts Kira, and has the Defiant beam the bomb into space, where it explodes harmlessly. As they start to get up, Dax tosses the last tribble in her hand down, where it falls through the doorway and onto Kirk, causing him to ask in anguish, "Close that door!"

Sisko tells the investigators that after the bomb exploded history continued uninterrupted and, thanks to a tribble's characteristic "alarm chirps", and McCoy's tricorder scans, Kirk exposed Darvin as a Klingon agent exactly as he had done before. By the time the DS9 personnel returned to the Defiant, Kira had figured out how to use the Orb to return the ship back to its proper time. Back in Sisko's office, the investigators ask if that is when they returned to the future, but Sisko is forced to admit that it was not, as he realized that there was one more thing he had to do – something he had thought of since he first saw the Enterprise on the Defiant's viewscreen. Sisko goes to the Enterprise's bridge and brings a duty roster to Kirk for the latter's approval. As Kirk looks it over, he looks over at Sisko, and asks his name. Sisko tells Kirk his real name and says that he has been on temporary assignment on the Enterprise. Before Sisko left, he just wanted to tell Kirk it was an honor serving with him. Kirk smiles, nods at him and then tells Sisko, "All right, lieutenant, carry on." Sisko thanks the legendary captain and leaves the bridge, while Spock and Uhura watch.

Back in his office, Sisko tells Dulmur and Lucsly that if they want to put a reprimand in his file for that, then they are welcome to do so. They both stand up and tell Sisko they will have to review everything before making a final recommendation, but it does not seem as if any harm was done. Dulmur says he probably would have done the same thing himself, given the chance. Sisko walks them out of the office; Lucsly tells them he will have their full report in about a month, but that he should have nothing to worry about. Sisko admits he is happy to hear it, and the investigators then quietly leave the station, heading directly for their ship at Docking Port Seven. Dax asks Sisko if it went well; he says it did. Kira tells Sisko that Odo wants to see them on the Promenade.

Odo asks Sisko if he told the investigators; Sisko says they did not ask, and that he is open to suggestions. Dax quips that they could build a new station. It turns out that Odo brought his tribble back with him, and it reproduced. True to Worf's warnings about them, a considerable number of the creatures are now all over the Promenade (particularly Quark's Bar, with one even sitting on Quark's head).

- Dax and Sisko, as the Defiant viewscreen clears to reveal the legendary ship

"Be specific, captain – which Enterprise? There have been five."
"Six."
"This was the first Enterprise, Constitution-class."
"His ship."
"James T. Kirk."
"The one and only!"
"Seventeen separate temporal violations – the biggest file on record."
"The man was a menace."

"Wait a minute, aren't you two wearing the wrong color?"
"Don't you know anything about this period in time?"
"I'm a doctor, not an historian!"
"In the old days, operations officers wore red, command officers wore gold..."
"...and women wore less."
"I think I'm going to like history."

"Oh, another glorious chapter in Klingon history. Tell me, do they still sing songs of 'The Great Tribble Hunt?'"

- Odo to Worf, on the destruction of the tribbles' homeworld

"I had no idea.""What?""He's so much more handsome in person. Those eyes!""Kirk had quite the reputation as a ladies' man.""Not him...Spock."
(Sisko quickly shuts the panel he's pretending to work on and starts pushing Dax away) "Let's go."

- Dax and Sisko

"I can't wait to get back to Deep Space 9 and see your face when you find out that I never existed!"

"They are Klingons... and it is a long story."
"What happened? Some kind of genetic engineering?"
"A viral mutation?"
"We do not discuss it with outsiders."

- Worf, O'Brien, and Bashir, when the lack of cranial ridges on Kirk-era Klingons is noted (see Klingon augment virus)

"Who started the fight?"
"I don't know, sir."

- Kirk questioning O'Brien, who lies

"I lied to Captain Kirk! I wish Keiko could have been there to see it."

- O'Brien, to Bashir

"McCoy... Leonard McCoy!... I met him when he was a student at Ole Miss... I had a feeling he'd become a doctor – he had the hands of a surgeon."

- Dax, recognizing an old friend on the Enterprise bridge

"I don't think we'll be able to access the internal sensors on board K-7."
"Then you will have to manually scan every tribble on the station."
"Well, there must be thousands of them by now!"
"Hundreds of thousands."
"One million, seven hundred seventy-one thousand, five hundred sixty-one. That's starting with one tribble with an average litter of ten every twelve hours. After three days –"
"Thank... you."

- O'Brien, Sisko, Bashir, and Dax, during the briefing about the tribble bomb

"There must be thousands of them!"
"Hundreds of thousands."
"One million, seven hundred seventy-one thousand, five hundred sixty-one. That's assuming one tribble, multiplying with an average litter of ten, producing a new generation every twelve hours over a period of three days–"
"And that's assuming that they got here three days ago–"
"ALSO allowing for the amount of grain consumed and the volume of the storage compartment–"

"Trials and Tribble-ations" was conceived as a tribute to TOS, broadcast to coincide with Star Trek's 30th anniversary. When Paramount asked executive producer Ira Steven Behr to come up with a suitable story to mark the event, he and the writing staff of Deep Space Nine gathered together and began brainstorming for plot ideas. Behr toyed with the notion of harkening back to the episode "Charlie X", since that installment was a favorite of Behr's and because actor Robert Walker – who had guest-starred as Charles Evans in the TOS episode – was still available. Skeptical that Walker would be interested in returning to Star Trek, this concept was discarded. (Star Trek Magazine issue 123, pp. 79–80)

When the writers sat down to decide which episode to use, there was little question that "The Trouble with Tribbles" was not only arguably the most famous TOS episode but also an excellent choice in that it was relatively lighthearted compared to other well-known episodes such as "The City on the Edge of Forever". In what Ira Steven Behr later described as the most incredible coincidence he has ever experienced, Behr and the other producers were at a pizza parlor in Beverly Hills, discussing the possibility of bringing original TOS actors back for this episode, when he recognized Charlie Brill (Arne Darvin). Although Behr was hesitant to discuss the matter directly with Brill (due to the complications that normally entail Hollywood negotiations), Brill was greatly honored to be given a chance to make history twice and felt that Gene Roddenberry would be proud. Behr later joked, in a DVDaudio commentary for this episode, that the remarkable turn of events proved God was a DS9 fan, while Brill stated that he was happy he hadn't gone out for Chinese food instead.

Worf faces "the big question"

The difference in appearance of TOS and TNG/DS9/VOY Klingons, first recognized as canon here (it was not broached in the DS9 second season episode "Blood Oath"), was addressed in the Star Trek: Enterprise episodes "Affliction" and "Divergence". There was a conscious effort to keep Worf at a distance from TOS-era Klingons due to the obvious make-up differences. Ronald Moore wrote Worf's explanation (or lack thereof) into the script because he felt that there was "not a single explanation that's less than preposterous" for the make-up differences and he believed that fans could figure out why the Klingons looked so different. Bashir and O'Brien's dialogue concerning the issue had them suggesting reasons, "genetic engineering" or "viral mutation", that had long been proposed by fans as the reasons for the differences. When the Enterprise episodes were filmed, the final canon explanation for the difference combined both their suppositions.

Ronald D. Moore's original idea for the episode was later picked up by Star Trek: Voyager in the episode "Virtuoso", although being set in the Delta Quadrant, contact with the Iotians was a physical impossibility. Instead, the crew stumble upon a technologically advanced culture which lacks the concept of music; fascinated by The Doctor's singing, the aliens begin to idolize him.

The writers were initially skeptical about whether creating an episode such as this with the relatively limited budget of a television series would be possible. However, when the visual effects team showed them a clip from "The Trouble with Tribbles," they were unable to tell that an extra person had been added to the scene because the blending was so seamless.

Contrary to the normal technique of chroma key (better known as "blue screen" or "green screen") shooting, in which the new footage is shot with a blue or green background in order to allow the computer to easily place the characters into another piece of footage, the scene in which Dax and Sisko are working behind Kirk and Spock was shot with an actual set background and then placed into the existing footage. This was due to the fact that there was no panel for Sisko and Dax to pretend to repair in the original shot.

Creating the footage for scenes such as the fight with the Klingons took almost a full week to shoot due to the number of components involved, the complexity of staging, and other minor details.

More crude blue screen techniques had actually already been employed in the Star Trek franchise for combining new performances with pre-existing footage; it had been employed previously in the Orlando, Florida venue of the Star Trek Adventure live-performance attraction.

Everything from the TOS sets was created faithfully right down to the blinking lights on the bridge, which the crew recreated by freeze-framing and painstakingly examining the TOS footage. Everything from the turbolift control panels to the wall intercoms to basic surface textures and back-lit graphics in the corridors were reproduced exactly as they originally appeared. Even the pattern of the overhead graphics in the Enterprise corridors is identical to the original.

However there were some minor details that didn't come out as planned. In the novelization, David Gerrold – who wrote the original Tribble-episode – spoke about the production in the preamble. Among other things he tells how Bob Justman pointed out that both the panelling and orange frames across from some ladder were not right. Michael Okuda explained that those were the only two things they could not perfectly recreate, as the company that made the reflective plastic had gone out of business ten years earlier and that nobody else produced that kind.

The lights showing the movement when inside the turbolift are considerably faster in the original series than in this episode.

The original Enterprise, now in the Smithsonian museum exhibit, had been refurbished and altered slightly over the years. Knowing that fans would inspect every minor detail of this episode for consistency, the staff consulted sketches made for the original series and had a special set of plans made for the new model's construction. They even inspected it with a magnifying glass to ensure that everything was perfect.

The original model of space stationK-7 had been lost by the time this episode was made. The recreation used in the new footage was created as faithfully as possible by watching the original episode as any fan might.

The clip featuring Sisko meeting Kirk was created with footage from "Mirror, Mirror" rather than "The Trouble with Tribbles", taking Kirk's introduction to the prime universe Marlena Moreau and inserting Sisko in Moreau's place.

Sisko's comment about asking Kirk about fighting the Gorn on Cestus III is a reference to "Arena".

In the original episode, when Kirk opens the door to the cargo hold and is pelted with tribbles, a tribble occasionally lands on him every minute or so even after all the tribbles would have fallen out. It is in this episode that the reason is learned: Sisko and Dax are hiding in the cargo hold, scanning all the tribbles and then tossing them out the door.

When Kirk sits on the tribble in his captain's chair, Dax is standing right where he looks, and shrugs sympathetically toward him. In "Trials and Tribble-ations: Uniting Two Legends", a featurette on the DS9 Season 5 DVD, Terry Farrell claims that director Jonathan West insisted, much to her delight, that the glance be as short as possible, since, if it went on too long, the audience would be hard-pressed to believe that Kirk would not make a point of introducing himself to such a beautiful young officer new to his ship.

In relation to making the show "feel" as close to the spirit of the original as possible, Ronald D. Moore has commented, "My only real gripe was the music – I had hoped it would be more like the original score and I thought it hurt the show particularly during the barroom brawl by changing the tone of the scene. Rene and I also had this idea to redo the entire end title sequence as an homage to the original series, with freeze frame shots from various DS9 episodes in the background, the TOS end credit music and changing the font of our credits to match theirs. That idea never got very far chiefly because we were the only proponents of it and also because the show was so far over budget that we couldn't afford to spend any more money anyway." (AOL chat,1997) To date, the only episodes of a Trek show to have changed title and credit sequences for a specific episode have been the mirror universeStar Trek: Enterprise episodes "In a Mirror, Darkly" and "In a Mirror, Darkly, Part II".

Moore also stated that as of the end of Season 5 of the show, this was the most expensive one-hour episode produced. (AOL chat,1997)

Here is an example of the "Forrest Gump" technique. The first image is the original from "The Trouble with Tribbles", the second is the altered version from this episode. The third image is the original from "Mirror, Mirror", the fourth is the altered version from this episode:

Once this episode was green-lit, an immediate question faced by the production staff was when it would air. The actual 30th anniversary of Star Trek was 8 September1996, but if the show aired that week, it would make it the first episode of the fifth season. The producers discussed the possibility of showing this episode as a kind of stand-alone show before returning to established chronology the following week with "Apocalypse Rising" but they ultimately decided to abandon this idea. (Star Trek: Deep Space Nine Companion)

Jonathan West directs Alexander Siddig on set

On the set of "Trials and Tribble-ations"

The producers specifically chose Jonathan West to direct this episode due to his cinematography training. According to West, he shot the episode as if it were actually 1967, with sixties style lenses and lighting techniques. He also used a sixties film stock with a finer grain and a different color saturation from that used in the nineties. (Star Trek: Deep Space Nine Companion)

In "Trials and Tribble-ations: A Historic Endeavor", a featurette on the DS9 Season 5 DVD, production designer Herman Zimmerman explains that he had just returned to Deep Space Nine from working on Star Trek: First Contact as "Trials and Tribble-ations" was going into early pre-production. Zimmerman noticed that the art department was drawing up construction plans so as to build the Enterprise sets by using the only floor plans that they could find on the Paramount lot. However, these plans had an incorrect scale which put the Enterprise's corridors at seven and a half feet wide, when Zimmerman knew they were actually twelve feet wide. He points out that if he hadn't returned at that moment, all of the Enterprise sets would have been in ⅝ scale.

According to Terry Farrell, it was easier to interact with stock footage than real people, due to the fact that they could watch the existing footage and observe exactly what the other person would be doing in the scene.

Jadzia Dax's enthusiasm about the 23rd century and her desire to revisit old friends was the writers' avenue by which to convey their own enthusiasm about writing the episode. It was also intended to represent the way fans of TOS would feel when watching the fusion of past and present Trek series.

When Jadzia and Benjamin Sisko enter the corridor aboard the USS Enterprise, the reactions from the actors are genuine, as they had not been on the set prior to that shot and were truly amazed by how faithfully the set recreated the look and feel of TOS. According to Terry Farrell, "What was great was that we were supposed to react to the sets like, 'Wow, we're on the Enterprise!' And it was easy because we felt like, 'Wow, we're on the Enterprise!' It looked so real!" This technique is commonly used in Hollywood; for example, two performers whose characters will be meeting for the first time may be kept separate prior to filming in order to evoke a more genuine reaction (a good example is William Petersen and Tom Noonan in Michael Mann's 1986 film Manhunter – they didn't actually meet one another until principal photography wrapped). Director Winrich Kolbe employed this technique during the shooting of the sixth season episode "The Sound of Her Voice", where he did not allow Debra Wilson to meet any of the recurring cast until after the shoot was completed.

The scene in which Dax is on the bridge of the Enterprise took twelve takes because of the complexity involved in the timing of the shot.

Reportedly, the DS9 stunt crew had both a challenge and a "good time", adjusting to the 'old-school' brawling style used in this episode's fight scenes.

The film elements from the original "Trouble With Tribbles" episode were used and transferred digitally, instead of using the 1980s analog flying-spot scanned transfers that were on professional format 1 inch Type C open reel videotape, so that there wouldn't be a difference in quality between the original scenes and the new Deep Space Nine scenes, especially for scenes where the characters from both shows were in the same shot. (DS9 Season 5 DVD)

Ira Steven Behr commented "The episode was just an amazing, amazing amount of work. The crew, the technical people, the actors – they just threw themselves into it. They were all having fun. Just sitting on those sets, being on that bridge. It was a hoot, a real hoot. Everyone who worked on it should be credited. The enthusiasm was like a little virus that just kept spreading. It's very rare in television, where you're fighting the clock and you have to produce so much in a limited amount of time, to really lavish the care on an episode the way we did on this. The only regret I have is that we can't lavish that time and attention on every single episode". (The Magic of Tribbles: The Making of Trials and Tribble-ations)

Although he was thrilled with how the episode turned out, with the high ratings it received and with the critical plaudits it garnered, there was one thing that Ira Steven Behr wasn't completely happy about; "the only thing that bugs me about it is that it feeds off the myth of the franchise, and the fact that it's so popular saddens me in a way, in the sense that I wish a show that is Deep Space Nine intensive didn't have to lean on the history." (Star Trek: Deep Space Nine Companion)

Alexander Siddig commented that he found "Trials and Tribble-ations": "a particularly fun show, like the Bond show. I felt like I'd taken on another character. Bashir wasn't the usual Bashir. And it was wonderfully strange to see myself acting with William Shatner. The technology is amazing isn't it?" ("A Truly Model Doctor", Star Trek Monthly issue 30)

When Sisko, O'Brien, and Bashir appear in the hallway of the USS Defiant in their 23rd century uniforms, Bashir thinks that Sisko and O'Brien have put on the wrong shirts because of the color, noticing that in the 23rd century, the command and engineering colors were reversed. O'Brien says, in effect, "Don't you know why?" to which Bashir responded "I'm a doctor, not an historian!"

Odo makes a comment to Worf about humanoids liking small furry animals, especially if they make a pleasing sound. A similar line was used by Leonard McCoy in the original episode.

According to Dulmur and Lucsly, this episode takes place "one hundred and five years, one month, and twelve days" after the events of "The Trouble with Tribbles".

Quark appeared in this episode (as an homage to the similarly tribble-covered bartender in the original episode) but Armin Shimerman has no spoken lines. This is the only episode of DS9 where Quark appears, but has no dialogue.

The names of the temporal investigators, Dulmur and Lucsly, are anagrams of "Mulder" and "Scully", the paranormal investigators of The X-Files (or, in the case of Dulmur, a near-anagram). Indeed, when meeting Sisko in his office Dulmur tells him he wants "the truth", while Lucsly is mostly skeptical about elements of Sisko's story. The writers considered having one of the characters deliver the line "The truth is out there". (The Magic of Tribbles: The Making of Trials and Tribble-ations)

The term "D7", in reference to the original Klingon battle cruiser, started out as an inside joke between William Shatner and Leonard Nimoy. It eventually became a reference to this style of battleship, but it wasn't "official" until this episode. The designation had been used since 1979 in the game Star Fleet Battles for that particular class of ship.

As Dax tells Sisko about how much more handsome Spock was in the flesh, the Kirk-Baris dialogue in the background is actually taken from their later confrontation aboard the station after Cyrano Jones had been detained.

Also regarding the comment by Dax regarding Spock's looks, it is curious that this seems the first time a Dax has seen Spock in person. Both were actively involved with the Khitomer accords, but being at that time the womanizer Curzon, he may have never considered or even noticed Spock's handsomeness, and so the symbiont Dax could barely have a memory of him other than a high-ranked male Vulcan. Instead, it is the first time Jadzia has seen Spock in person.

In the same scene, Odo's failure to immediately realize that Freeman is not the captain is somewhat incongruous; since he had been in the bar beforeChekov and Uhura, who had entered just as Kirk and Spock were leaving, he and Kirk must have been in the bar at the same time.

The number of tribbles that Dax calculates is the same number that Spock determined in the original episode.

Darvin, posing as Barry Waddle, claims he deals in (among other things) kevas and trillium, the two materials Spock claimed he dealt in while posing as a Vulcan trader in TOS: "Errand of Mercy".

Worf (slightly younger than he is here) met an older Scotty 101 years later, while serving aboard another Enterprise in TNG: "Relics". O'Brien was also serving aboard that Enterprise at the time, though it's not known if he and Scotty ever actually met.

Sisko states that if he could (without causing harm to the timeline), he would ask Kirk about his confrontation with the Gorn on Cestus III, in TOS: "Arena". Worf already had something of a similar opportunity when Dax introduced him to Kor in DS9: "The Sword of Kahless", mentioning, among other things, his confrontation with Kirk on Organia in TOS: "Errand of Mercy".

Dax claims that Koloth once told Curzon that he regretted not facing Captain Kirk in battle. However, in TAS: "More Tribbles, More Troubles", Koloth fought the Enterprise several times. This may be due to the fact that The Animated Series was officially declared "non-canon" by Paramount despite TAS references being worked into the series, including the Edosian orchid in DS9: "Broken Link". A more benevolent reason could be that Koloth and Kirk in the TAS episode never had a REAL battle, just skirmishes and tricks. Koloth might also have been indicating a face-to-face, physical combat, rather than a clash of starships.

Sisko's line of "Storage compartments. Storage compartments." in the episode is the same as Kirk's line of "Storage compartments? Storage compartments?" from "The Trouble with Tribbles".

giving information about transparent aluminum to, Dr. Nichols the president of Plexicorp (although this can be attributed more to Scotty than Kirk, with Scotty speculating that they were merely preserving history by providing the original inventor the means to create it)

bringing two whales from the 20th century to save Earth from the cetacean probe

Temporal Investigations may not know about this, as McCoy may be unaware his phaser went missing and a homeless man killed himself with it

taking work, money, housing and food that others would otherwise have consumed

after Kirk saved the USS Enterprise-B from being destroyed in the Nexus, he was swept into the energy ribbon. Although from his point of view, Kirk was altering future events, he technically went into the past by agreeing to assist Captain Picard stop Soran. However, Picard altered past events by preventing the destruction of the Veridian System and the survivors of the USS Enterprise-D. Kirk would have known that by leaving the timeline, he would be assisting Picard alter the timeline by preventing the torpedo launch.

David Gerrold, writer of "The Trouble with Tribbles", can be seen in two scenes, playing an Enterprise crewman (he is the gray-haired man who passes Sisko and Dax when the Enterprise goes to red alert). Bashir and O'Brien later see him petting a tribble in the corridor (which, in actuality, is an original tribble used in "The Trouble with Tribbles"). Gerrold thought the episode was "one of the cleverest Star Trek scripts I've ever read."

The permission of the TOS actors had to be sought to use their performances in the various episodes the archive footage was taken from. It took the producers three months to negotiate for the use of the footage. Walter Koenig remarked he was paid "eight times more" for the use of his likeness than he was for the original episode.

This episode was nominated for the 1997 Hugo Award for Best Dramatic Presentation. It was also nominated for three Emmy Awards for Outstanding Individual Achievement in Special Visual Effects, Outstanding Art Direction for a Series, and Outstanding Hairstyling for a Series (which was won by VOY: "Fair Trade").

Paramount announced the HD remastered version of this episode would be included on the TOS Season 2 Blu-ray collection. [1] The episode was presented in a 16:9 matte preserving its 4:3 ratio with 480i video, but encoded in VC-1.